Freeview modes
Brian Butterworth published on UK Free TV Two of the Freeview multiplexes (collections of channels) broadcast in one mode known as "64QAM mode, FEC=2/3,", and the other three broadcast in another mode called "64QAM mode, FEC=3/4".
The " FEC=2/3" mode provide a more reliable signal than a "FEC=3/4" mode signal at the same power level, but there is a trade-off that means less digital data can be carried.
This diagram shows the current channels carried on the Freeview system. The wider the box, the more bandwidth is used to carry the pictures. The more bandwidth used for a service, the better the picture quality.
Boxes split horizontally denote channels that occupy the bandwidth at different times of the day.
The third line shows the configuration of the BBC "B" multiplex switchover which is used for HD and is in another mode DVB-T2 256QAM.
64 QAM (3/4) mode
In this mode, the digital TV signal is transmitted in groups of 64 symbols. The "forward error correction" is 2/3, and this results in a bitrate of 24M.1b/s (megabits per second). This can be used to carry up to eight simultaneous television channels.64 QAM (2/3) mode
In this mode, the digital TV signal is transmitted in groups of 16 symbols. The "forward error correction" is 3/4, and this results in a bitrate of 27.1Mb/s. This can be used to carry ten simultaneous television channels.Help with Television sets?
Tuesday, 12 July 2011
M
Mark2:46 PM
Faringdon
My Freeview reception comes from the Oxford transmitter.The reception has always been variable due to a hill being in direct line of site between my house and Oxford.I was hoping that after the switchover in September, the picture would improve with a much stronger signal(up to nine times stronger?), but I have now read that the transmitter will be restricted to 12KW instead of 75KW after the switchover. Does anyone know why and for how long.
Regards Mark
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Mark's: mapM's Freeview map terrainM's terrain plot wavesM's frequency data M's Freeview Detailed Coverage
M
Mike Dimmick3:04 PM
Mark: The three public-service multiplexes - which carry the BBC channels, the primary ITV and Channel 4 channels, Channel 5, and the HD channels - will broadcast at 100 kW from 14 August (BBC SD channels)/28 August (other channels).
The other three, commercial, multiplexes, will ultimately transmit at 50 kW. They are restricted to 12.5 kW until 18 April 2012. This is when the Crystal Palace transmitter group completes switchover. We haven't been given reasons for the power restrictions, but you can often figure it out by looking at the maps of other transmitters using the same frequencies. My guess is that this is to protect viewers of the High Wycombe transmitter, although this will continue to use these channels after switchover. Some of Hannington's north-western relays (Lambourn, Chisbury, Hemdean) also use these channels, and are moving to different channels at switchover. However, Hannington's switchover is in February.
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Friday, 29 July 2011
K
Kevin8:42 PM
I am on the Wrekin transmitter and I can get most channels except those on MUX C. Is there something I need to do to be able to receive these..?
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Tuesday, 2 August 2011
Kevin: Please see Single frequency interference | ukfree.tv - independent free digital TV advice . I can't be more specific without a full postcode.
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Tuesday, 9 August 2011
Tim
10:18 PM
Dartmouth
10:18 PM
Dartmouth
At 9pm ALL my limited set of freeview channels from the Dartmouth transmitter degrade to unwatchable. As time passes the degradation increases. This has repeated every night for the last several nights. We know that, at 9pm, this will happen.
Clearing out the freeview channels and retuning has no effect, with of without hard power reset. I use a freeview enabled TV, not a set top box. TQ6 9PQ is the full postcode
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Tim's: mapT's Freeview map terrainT's terrain plot wavesT's frequency data T's Freeview Detailed Coverage
Wednesday, 10 August 2011
Tim
10:18 PM
10:18 PM
I did, Briantist. I can identify nothing nearby. Not in my home nor in my neighbours' homes. There are no devices such as those listed.
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Thursday, 11 August 2011
T
Tim8:34 PM
Hi,
I'm actually writing from northern Spain. I recently had a new digibox installed as I could hardly see anything without interference. Now I've got all the regional BBCs and ITVsbut strangely there is no BBC3 or BBC4 and no CITV. As far as i can see these are the only channels missing. Any ideas?
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Monday, 15 August 2011
Tim: Sorry for not getting back sooner. You would expect the services you list to disappear first, as these are on the Astra 2D satellite, which has a "footprint" that is focused on the UK.
You need a large dish to get these services in the first place, and any slight misalignment will make them disappear. You probably just need to have your dish correctly realigned on the Astra 2D satellite.
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Tim: You might need to get a professional in to make measurements. You might also like to suspect a faulty streetlight (or similar) - these are often the cause of night-time interference.
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